Engine Oil: Difference between Single Grade Oil and Multigrade Oil

A quality characteristic of motor oil is, whether the oil is a single or a multi-grade oil.

Normal oil is inherently subject to certain chemical and physical properties. One is that the condition of the oil is highly dependent on the temperature: the more warmer it is, the thinner and more flexible is the oil. If it is cold instead, the oul is thick and viscous.

In former times when using old mineral oils, this made it neccessary to change the oil in spring and automn in order to prepare for the temperatures in summer and winter.

Today's oils (synthetic oils) contain numerous additives and for the production, other artificial improved base oils are used, making the oil more independent of the outside temperature. The modern synthetic oil keeps its properties both in winter and in summer.

With the terms single grade oil and multigrade oil, exactly this difference is identified. The old oils were suitable only for "a grade", while the new varieties for can be used for "multiple grades".